Carburetor with power choke

ABSTRACT

A multiple stage internal combustion engine carburetor has an electrically heated power element which positions a fast idle lever to control engine idle speed and which positions a power element lever that acts through a spring operated intermediate lever to position the choke valve. A vacuum break mechanism and a wide open kick tang on a primary throttle lever act on the intermediate lever to open the choke, and a secondary throttle lockout lever is actuated by the power element lever.

United States Patent 1 Brown, III et al.

[ CARBURETOR WITH POWER CHOKE [75] Inventors: Reed M. Brown, III, Fairport;

Donald D. Stoltman, Henrietta, both of NY.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

221 Filed: Oct. 7, 1971 21 App]. No.: 187,352

[52] U.S. Cl 261/23 A, 261/39 A, 261/52 [51] Int. Cl. F02m 1/12 [58] Field of Search 261/23 A, 39 A, 52

[56] References Cited UNITED STATES PATENTS 3,291,462 12/1966 Mennesson 261/39 A 1 June 19, 1973 4/1971 Goto et al 261/39 A 2/1972 Eckert et al. 261/39 A Primary Examiner-Tim R. Miles Attorney .l. L. Carpenter and C. KI 'vee'ns'ira' [57] ABSTRACT A multiple stage internal combustion engine carburetor has an electrically heated power element which positions a fast idle lever to control engine idle speed and which positions a power element lever that acts.

7 Claims, 2 Drawing Figures PATENIEB 9975 S m Mu M 6 w CARBURETOR WITH POWER CHOKE This invention relates to a mechanism for controlling the position of choke and throttle valves in an internal combustion engine carburetor. More particularly, it is directed to a mechanism in which a power element, particularly one heated electrically, controls the positions of a plurality of levers in a compact arrangement thatincorporates all the functions provided by conventional automatic choke mechanisms which are operated by a coiled bimetallic strip responsive to engine temperatures.

The details as well as other objects and advantages of this invention are set forth below and shown in the drawings in which:

FIG. 1 is a side elevational view of a carburetor equipped with this power choke mechanism, portions being broken away to show details of the power element construction; and

FIG. 2 is an end view of the power choke mechanism taken generally as indicated along line 2-2 of FIG. 1.

Referring to the drawings, a carburetor has one or more primary mixture conduits l2 and one or more secondary mixture conduits 14. A choke shaft 16 is rotatably disposed in primary mixture conduit 12, and a round choke valve blade 18 is secured on choke shaft 16 to control air flow into primary mixture conduit 12.

A primary throttle shaft 20 also is rotatably disposed in primary mixture conduit 12, and a primary throttle valve blade 22 is secured on primary throttle shaft 20 to control air and fuel flow from primary mixture conduit 12. Similarly, a secondary throttle shaft 24 is rotatably disposed in secondary mixture conduit 14, and a secondary throttle valve blade 26 is secured on secondary throttle shaft 24 to control airand fuel flow from secondary mixture conduit 14.

An enclosure 28, which is either a portion of the fuel bowl section casting or a separate casting secured thereto, contains a power element 30. Power element 30 includes a cup 32 containing a mass of thermally expansible material 34, such as wax or oil, which is enclosed by a seal 36. A backing member 38 retains seal 36 within cup 32 and closes the open end of cup 32. If desired, backing member 38 may include a plastic bearing surface member 40 for the purposes which will be evident below.

A plunger 42 extendsthrough an opening 44 in backing member 38 and is received by seal 36. Upon thermal expansion of material 34, backing member 38 and cup member 30 are axially displaced with respect to plunger 42, plunger 42 remaining immobile due to its abutment with adjusting screw 46 threadedly received by enclosure casting 28.

Power element 30 is received in a heater assembly 48. Heater assembly 48 includes a cupped aluminum housing 50 spaced from the sides of power element cup 32 by a sleeve 52 of Mylar which thermally and electrically insulates the sides of cup 32. The bottom of cup 50 contains a copper disc 54 and a sintered barium titanate heating disc 56. Cup 50 and thus disc 56 arebiased against cup 32 of power element 30, and thus power element assembly 30 is biased leftwardly, by a spring 58 which seats between a flange 60 on cupped housing 50 and an annular portion 62 of an electrical terminal 64. Terminal 64 is secured in place, and power element assembly 30 and heater assembly 48 are enclosed within enclosure 28, by a cover 66 retained by a bail 68.

Upon closure of the ignition, oil pressure or the like switch 70, current is provided through terminal 64, spring 58, cupped housing 50, copper and barium titanate discs 54 and 56, power element cup 32, backing member 38, and a light spring 72; to enclosure casting as which is grounded through the engine block. Current flow through disc 56 increases its temperature and causes it to heat power element 30. Disc 56 has a resistance of perhaps 25 ohms at 77 F., which resistance increases only gradually until the temperature approaches 250 F. and increases very rapidly above 250 F. Thus heat is provided to power element 30 until the temperature of disc 56 reaches about 250 F., and thereafter the current passing through disc 56 is only sufficient to maintain a temperature of about 250 F. A period of perhaps 4 minutes may be required for the temperature to increase from 0 to 250 F. Over that temperature range, the material 34 will expand suffi ciently to displace cup 32 and backing member 38 less than approximately one-half inch with respect to plunger 42.

An intermediate shaft 74 is secured against rotation in carburetor l0, and a power element lever 76 and an intermediate lever 78 are journalled on intermediate shaft 74. Intermediate lever 78 has an arm 80 connected by a link 82 to a lever 84 secured to choke shaft 16 whereby clockwise movement of intermediate lever 78 causes opening movement of choke valve 18. A choke closing torsion spring 86 is wound about intermediate shaft 74 and has one end 88 hooked over an arm 90 of power element lever 76 with the opposite end 92 hooked through a slot 94 in intermediate lever 78. Torsion spring 86 biases power element lever 76 counterclockwise to cause a tang 96 on arm 90 to engage the plastic bearing portion 40 of backing member 38 and biases intermediate lever 78 counterclockwise to close choke valve 18. It will be noted that during decreasing temperatures, with the concomitant contraction of thermally expansible material 34, spring 58 will cause leftward movement of power element assembly 30 and counterclockwise movement of power element lever 76 to increase the choke closing force of torsion spring 86.

A second torsion spring 98 also is wound about inter mediate shaft 74 and has one end 100 hooked over a stationary abutment, here indicated for example as at 102, while the other end 104 is hooked over intermediate lever 78. Torsion spring 98 thereby exerts a light force on intermediate lever 78 tending to open choke 18. Actually, however, the force: exerted by torsion spring 98 is insufficient to overcome the force of either torsion spring 86 or power element spring 58. Thus torsion spring 98 effectively only acts through intermediate lever 70 and torsion spring 86 to bias power element lever 76 against bearing plate portion 40 of power element backing member 38.

It will be appreciated, therefore, that upon increasing temperatures, power element cup 32 and backing member 38 will move toward the right against the bias of spring 58, power element lever 76 will rotate clockwise, tending to relax the choke closing force of torsion spring 86, thereby permitting clockwise movement of intermediate lever 78 to allow opening movement of choke valve 18.

A vacuum break lever 106 is joumalled on a vacuum break shaft 108 secured in carburetor 10. A vacuum break unit 110, acting through a link 112, causes counterclockwise movement of vacuum break lever 106, and a tang 114 on vacuum break lever 106 engages either arm 80 of intermediate lever 78 or a turned end of link 82 to cause opening movement of choke valve 18.

Secondary throttle shaft 24 has a pin 116 which engages in a notch 118 of a secondary throttle lockout lever 120 journalled on a lockout shaft 122 secured in carburetor 10. In the position shown, engagement of pin 116 in notch 118 prevents opening movement of secondary throttle valve 26. As power element cup 32 and backing member 38 move rightwardly to the fully warmed position, clockwise rotation of power element lever 76 brings a tang 124 thereof into engagement with a tang 126 on lockout lever 120. The resulting counterclockwise rotation of lockout lever 120 moves lockout lever 120 out of the path of pin 116 and permits counterclockwise rotation of pin 116 and secondary throttle shaft 24.

A primary throttle lever 128 is secured to primary throttle shaft 20 and is biased clockwise by the usual throttle return spring, here represented by 130. As primary throttle 22 approaches the wide open position, a wide open kick tang 132 on throttle lever 128 engages a tang 134 on intermediate lever 78 to cause clockwise, choke opening, movement of intermediate lever 78.

A fast idle lever 136 is journalled on primary throttle shaft 29 and has an arm 138 engaging bearing portion 40 of backing member 38. Fast idle lever 136 includes a tang 140 which is engaged by an idle speed adjusting screw 142 carried by a tang 144 on primary throttle lever 128.

It will be noted that power element assembly 30 is shown in the lowest temperature position whereby fast idle lever 136 has been rotated counterclockwise and is thereby acting through adjusting screw 142 to rotate primary throttle lever 128 counterclockwise, against the bias of return spring 130, to open primary throttles 22 to a fast idle position. As power element 30 is heated, cup 32 and backing member 38 will move rightwardly to allow clockwise movement of fast idle lever 136 and primary throttle lever 128, thereby moving primary throttle 22 toward a closed position to reduce engine idle speed;

From the foregoing, it will be appreciated that this invention has provided a power choke mechanism which is compact and yet which provides all of the functions expected of a modern automatic choke mechanism.

We claim:

1. A carburetor comprising a mixture conduit, a choke shaft rotatably disposed in said mixture conduit, a choke valve secured on said shaft, a choke lever secured to said choke shaft, a power element having a cup member open at one end, a mass of thermally expansible material disposed in said cup member, a seal enclosing said material in said cup member, a backing member retaining said seal in said cup member and closing the open end of said cup member and having an opening, and a plunger extending through said opening and received by said seal, said backing and cup members being axially displaceable from said plunger upon thermal expansion of said material, an intermediate shaft, a power element lever rotatably mounted on said intermediate shaft, an intermediate lever rotatably mounted on said intermediate shaft, a link connecting said intermediate lever and said choke lever, a choke closing torsion spring disposed about said intermediate shaft and having one end connected to said intermediate lever and the other end connected to said power element lever whereby said power element lever is biased into engagement with said backing member and whereby said intermediate lever, said link, and said choke lever are biased in a choke valve closing direction, a choke opening torsion spring disposed about said intermediate shaft and having one end connected to an abutment and the other end connected to said intermediate lever whereby said intermediate lever, said link, and said choke lever are biased in a choke valve opening direction, and a power element spring biasing said backing and cup members against axial displacement from said plunger, whereby said backing and cup members and said power element lever are biased to increase the torsion of said choke closing spring to thereby bias said intermediate lever, said link, and said choke lever in a choke closing direction against the bias of said choke opening spring, and whereby upon thermal expansion of said material said backing and cup members are axially displaced from said plunger against the bias of said power element spring and said power element lever is moved to reduce the torsion of said choke closing spring to thereby permit the bias of said choke opening spring to move said intermediate lever, said link, and said choke lever in a choke opening direction.

2. The carburetor of claim 1 which further comprises a throttle shaft rotatably disposed in said mixture conduit, a throttle valve secured on said throttle shaft, and a throttle lever secured to said throttle shaft, said throttle lever having an arm engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction as said throttle lever is moved in a throttle opening direction.

3. The carburetor of claim 1 which further comprises a vacuum break shaft, a vacuum break lever rotatably mounted on said vacuum break shaft and engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction, and a vacuum break unit connected to said vacuum break lever for moving said vacuum break lever into engagement with said intermediate lever.

4. The carburetor of claim 1 which further comprises a throttle shaft rotatably disposed in said mixture conduit, a throttle valve secured on said throttle shaft, a throttle lever secured to said throttle shaft, and a fast idle lever rotatably mounted on said throttle shaft and engageablewith said throttle lever and said power element backing member to limit movement of said throttle lever in a throttle valve closing direction in accordance with the position of said backing member.

5. The carburetor of claim 1 which further comprises a secondary mixture conduit, a secondary throttle shaft rotatably disposed in said secondary mixture conduit, a secondary throttle valve secured on said secondary throttle shaft, a stop pin secured to said secondary throttle shaft, a lockout shaft, and a lockout lever rotatably mounted on said lockout shaft and engaging said stop pin to prevent movement of said stop pin in a secondary throttle opening direction, and wherein said power element lever includes means engageable with said lockout lever for moving said lockout lever out of engagement with said stop pin as said power element lever is moved to reduce the torsion of said choke closing spring.

6. The carburetor of claim 1 wherein said power element spring, said backing member, and said cup member are electrically conductive, and which further comprises an electrically conductive heating element disposed adjacent the opposite end of said power element cup member, an electrically insulating sleeve disposed about the sides of said cup member, an electrically conductive cupped housing enclosing said heating element and said insulating sleeve, said housing having a flange receiving said power element spring, and means for passing an electric current through said power element spring, said housing, said heating element, said cup member, and said backing member to energize said heating element and thereby cause thermal expansion of said thermally expansible material.

7. A carburetor comprising primary and secondary mixture conduits, a choke shaft rotatably disposed in said primary mixture conduit, a choke valve secured on said choke shaft, a choke lever secured to said choke shaft, primary and secondary throttle shafts respectively rotatably disposed in said primary and secondary mixture conduits, primary and secondary throttles respectively secured on said primary and secondary throttles, a primary throttle lever secured to said primary throttle shaft, a power element having a cup member open at one end, a mass of thermally expansible material disposed in said cup member, a seal enclosing said material in said cup member, a backing member retaining said seal in said cup member and closing the open end of said cup member and having an opening, and a plunger extending through said opening and received by said seal, said backing and cup members being axially displaceable from said plunger upon thermal expansion of said material, an intermediate shaft, a power element lever rotatably mounted on said intermediate shaft, an intermediate lever rotatably mounted on said intermediate shaft, a link connecting said intermediate lever and said choke lever, a choke closing torsion spring disposed about said intermediate shaft and having one end connected to said intermediate lever and the other end connected to said power element lever whereby said power element lever is biased into engagement with said backing member and whereby said intermediate lever, said ink, and said choke ever are biased in a choke valve closing direction, a choke opening torsion spring disposed about said intermediate shaft and having one end connected to an abutment and the other end connected to said intermediate lever whereby said Intermediate lever, said link, and said choke lever are biased in a choke valve opening direction, a power element sPring biasing said backing'and cup members against axial displacement from said plunger whereby said backing and cup members and said power element lever are biased to increase the torsion of said choke closing spring to thereby bias said intermediate lever, said link, and said choke lever in a choke closing direction against the bias of said choke opening spring, said backing and cup members being axially displaced from said plunger against the bias of said power element spring upon thermal expansion of said material and said power element lever being moved thereby to reduce the torsion of said choke closing spring and permit the bias of said choke opening spring to move said intermediate lever, said link, and said choke lever in a choke opening direction, said primary throttle lever having an arm engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction as said throttle lever is moved in a throttle opening direction, a vacuum break shaft, a vacuum break lever rotatably mounted on said vacuum break shaft and engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction, a vacuum break unit connected to said vacuum break lever for moving said vacuum break lever into engagement with said intermediate lever, a fast idle lever rotatably mounted on said primary throttle shaft and engageable with said primary throttle lever and said power element backing member to limit movement of said primary throttle lever in a primary throttle valve closing direction in accordance with the position of said backing member, a stop pin secured to said secondary throttle shaft, a lockout shaft, a lockout lever rotatably mounted on said lockout shaft and engaging said stop pin to prevent movement of said stop pin in a secondary throttle opening direction, said power element lever including means engageable with said lockout lever for moving said lockout lever out of engagement with said stop pin as said power element lever is moved to reduce the torsion of said choke closing spring, said power element spring, said backing member, and said cup member being electrically conductive, an electrically conductive heating element disposed adjacent the opposite end of said power element cup member, an electrically insulatinG sleeve disposed about the sides of said cup member, on electrically conductive cupped housing enclosing said heating element and said insulating sleeve, said housing having a flange receiving said power element spring, and means for passing an electric current through said power element spring, said housing, said heating element, said cup member, and said backing member to energize said heating element and thereby cause thermal expansion of said thermally expansible material. 

1. A carburetor comprising a mixture conduit, a choke shaft rotatably disposed in said mixture conduit, a choke valve secured on said shaft, a choke lever secured to said choke shaft, a power element having a cup member open at one end, a mass of thermally expansible material disposed in said cup member, a seal enclosing said material in said cup member, a backing member retaining said seal in said cup member and closing the open end of said cup member and having an opening, and a plunger extending through said opening and received by said seal, said backing and cup members being axially displaceable from said plunger upon thermal expansion of said material, an intermediate shaft, a power element lever rotatably mounted on said intermediate shaft, an intermediate lever rotatably mounted on said intermediate shaft, a link connecting said intermediate lever and said choke lever, a choke closing torsion spring disposed about said intermediate shaft and having one end connected to said intermediate lever and the other end connected to said power element lever whereby said power element lever is biased into engagement with said backing member and whereby said intermediate lever, said link, and said choke lever are biased in a choke valve closing direction, a choke opening torsion spring disposed about said intermediate shaft and having one end connected to an abutment and the other end connected to said intermediate lever whereby said intermediate lever, said link, and said choke lever are biased in a choke valve opening direction, and a power element spring biasing said backing and cup members against axial displacement from said plunger, whereby said backing and cup members and said power element lever are biased to increase the torsion of said choke closing spring to thereby biAs said intermediate lever, said link, and said choke lever in a choke closing direction against the bias of said choke opening spring, and whereby upon thermal expansion of said material said backing and cup members are axially displaced from said plunger against the bias of said power element spring and said power element lever is moved to reduce the torsion of said choke closing spring to thereby permit the bias of said choke opening spring to move said intermediate lever, said link, and said choke lever in a choke opening direction.
 2. The carburetor of claim 1 which further comprises a throttle shaft rotatably disposed in said mixture conduit, a throttle valve secured on said throttle shaft, and a throttle lever secured to said throttle shaft, said throttle lever having an arm engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction as said throttle lever is moved in a throttle opening direction.
 3. The carburetor of claim 1 which further comprises a vacuum break shaft, a vacuum break lever rotatably mounted on said vacuum break shaft and engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction, and a vacuum break unit connected to said vacuum break lever for moving said vacuum break lever into engagement with said intermediate lever.
 4. The carburetor of claim 1 which further comprises a throttle shaft rotatably disposed in said mixture conduit, a throttle valve secured on said throttle shaft, a throttle lever secured to said throttle shaft, and a fast idle lever rotatably mounted on said throttle shaft and engageable with said throttle lever and said power element backing member to limit movement of said throttle lever in a throttle valve closing direction in accordance with the position of said backing member.
 5. The carburetor of claim 1 which further comprises a secondary mixture conduit, a secondary throttle shaft rotatably disposed in said secondary mixture conduit, a secondary throttle valve secured on said secondary throttle shaft, a stop pin secured to said secondary throttle shaft, a lockout shaft, and a lockout lever rotatably mounted on said lockout shaft and engaging said stop pin to prevent movement of said stop pin in a secondary throttle opening direction, and wherein said power element lever includes means engageable with said lockout lever for moving said lockout lever out of engagement with said stop pin as said power element lever is moved to reduce the torsion of said choke closing spring.
 6. The carburetor of claim 1 wherein said power element spring, said backing member, and said cup member are electrically conductive, and which further comprises an electrically conductive heating element disposed adjacent the opposite end of said power element cup member, an electrically insulating sleeve disposed about the sides of said cup member, an electrically conductive cupped housing enclosing said heating element and said insulating sleeve, said housing having a flange receiving said power element spring, and means for passing an electric current through said power element spring, said housing, said heating element, said cup member, and said backing member to energize said heating element and thereby cause thermal expansion of said thermally expansible material.
 7. A carburetor comprising primary and secondary mixture conduits, a choke shaft rotatably disposed in said primary mixture conduit, a choke valve secured on said choke shaft, a choke lever secured to said choke shaft, primary and secondary throttle shafts respectively rotatably disposed in said primary and secondary mixture conduits, primary and secondary throttles respectively secured on said primary and secondary throttles, a primary throttle lever secured to said primary throttle shaft, a power element having a cup member open at one end, a mass of thermally expansible material disposed in said cup member, a seal enclosIng said material in said cup member, a backing member retaining said seal in said cup member and closing the open end of said cup member and having an opening, and a plunger extending through said opening and received by said seal, said backing and cup members being axially displaceable from said plunger upon thermal expansion of said material, an intermediate shaft, a power element lever rotatably mounted on said intermediate shaft, an intermediate lever rotatably mounted on said intermediate shaft, a link connecting said intermediate lever and said choke lever, a choke closing torsion spring disposed about said intermediate shaft and having one end connected to said intermediate lever and the other end connected to said power element lever whereby said power element lever is biased into engagement with said backing member and whereby said intermediate lever, said ink, and said choke ever are biased in a choke valve closing direction, a choke opening torsion spring disposed about said intermediate shaft and having one end connected to an abutment and the other end connected to said intermediate lever whereby said Intermediate lever, said link, and said choke lever are biased in a choke valve opening direction, a power element sPring biasing said backing and cup members against axial displacement from said plunger whereby said backing and cup members and said power element lever are biased to increase the torsion of said choke closing spring to thereby bias said intermediate lever, said link, and said choke lever in a choke closing direction against the bias of said choke opening spring, said backing and cup members being axially displaced from said plunger against the bias of said power element spring upon thermal expansion of said material and said power element lever being moved thereby to reduce the torsion of said choke closing spring and permit the bias of said choke opening spring to move said intermediate lever, said link, and said choke lever in a choke opening direction, said primary throttle lever having an arm engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction as said throttle lever is moved in a throttle opening direction, a vacuum break shaft, a vacuum break lever rotatably mounted on said vacuum break shaft and engageable with said intermediate lever for moving said intermediate lever, said link, and said choke lever in a choke opening direction, a vacuum break unit connected to said vacuum break lever for moving said vacuum break lever into engagement with said intermediate lever, a fast idle lever rotatably mounted on said primary throttle shaft and engageable with said primary throttle lever and said power element backing member to limit movement of said primary throttle lever in a primary throttle valve closing direction in accordance with the position of said backing member, a stop pin secured to said secondary throttle shaft, a lockout shaft, a lockout lever rotatably mounted on said lockout shaft and engaging said stop pin to prevent movement of said stop pin in a secondary throttle opening direction, said power element lever including means engageable with said lockout lever for moving said lockout lever out of engagement with said stop pin as said power element lever is moved to reduce the torsion of said choke closing spring, said power element spring, said backing member, and said cup member being electrically conductive, an electrically conductive heating element disposed adjacent the opposite end of said power element cup member, an electrically insulatinG sleeve disposed about the sides of said cup member, on electrically conductive cupped housing enclosing said heating element and said insulating sleeve, said housing having a flange receiving said power element spring, and means for passing an electric current through said power element spring, said housing, said heating element, said cup member, and said backing member to energize said heating element and theReby cause thermal expansion of said thermally expansible material. 